Glass used in windshields, windows and other openings of aircraft or automobiles not only has the function of protecting pilots and crew from outside airflow but also acts to screen out injurious solar rays and exclude solar heat from the interior of the vehicle.
The harmful rays contained in the solar radiation are mainly in the ultraviolet (UV) and infrared (IR) spectrum. A conventional optical filter for screening out both ultraviolet and infrared rays is composed of ultraviolet absorption glass coupled with infrared absorption glass. The ultraviolet absorption glass is produced by adding a certain of ultraviolet cut-off material into an ordinary glass to render the ultraviolet absorption glass capable of screening out the ultraviolet rays. The ultraviolet cut-off material is mainly composed of cerium hydrate and titanium oxide. The infrared absorption glass is produced by adding an amount of infrared cut-off material to an ordinary glass to render the infrared absorption glass capable of screening out the infrared radiation. The infrared cut-off material includes iron oxide or a compound containing iron oxide. In this conventional optical filter, the UV and IR radiations are screened out by the absorption agent, so a filtering quality of the optical filter is greatly limited. In addition, the conventional optical filter is made of two pieces of absorption glasses, thus rendering a complexity in structure.
Therefore, it is desired to provide an improved optical filter that overcomes the above-described problems.